Process for the production of renewable base oil, diesel and naphtha

ABSTRACT

Hydrotreatment of biological oil is disclosed for producing renewable base oil and a diesel oil from low value biological oils. Low value biological oils containing free fatty acids and fatty acid esters can be processed into a renewable base oil and a renewable diesel oil in an efficient manner by first separating at least part of the free fatty acids from the feedstock and then processing separately this free acid feed in a ketonisation reaction followed by hydrodeoxygenation and hydroisomerisation reactions to yield a renewable base oil stream. The remaining free fatty acid depleted feed is processed in a separate hydrodeoxygenation and hydroisomerisation step to yield a renewable diesel stream.

TECHNICAL FIELD

The present invention relates to the field of hydrotreatment ofbiological oil, in particular to methods for producing renewable baseoil and a diesel oil, such as methods for producing renewable base oil,a diesel oil and naphtha in a process efficient manner, and inparticular with reduced hydrogen consumption and increased catalyst lifetime.

BACKGROUND ART

The technology relating to hydrotreatment of biological oils, such asplant oils and animal fats has received much attention since thecombined steps of hydrodeoxygenation and hydroisomerisation of plantoils was first found to result in a renewable diesel with improved coldflow properties back in the last years of the 20th century. In thebeginning of the 21th century the manufacture of renewable base oil hasalso been investigated through a number of routes, including double-bondoligomerisation of renewable oils or ketonisation reactions of fattyacids.

The hydrotreatment of biological oils are for the most part catalysed.Catalytic hydrotreatment of biological oils on an industrial scale (>100kt biological oil annually) faces several challenges, such as the timethat the plant or reactor can remain on-stream before maintenance isrequired. One of the causes for reduced times on-stream is thedeactivation of the catalyst, or the physical plugging of the catalystbed, causing an increased and undesired pressure drop. The catalyst lifetime is highly dependent on the quality of the feedstock. One of thechallenges of catalytic hydrotreatment is the catalyst life time, inparticular in combination with the processing of more degraded feedscomprising glycerides together with certain amounts of more reactivefree fatty acids (FFA), compared to less degraded biological oils, suchas for example edible rapeseed oil, which has very low amounts of freefatty acids. Another challenge in the hydrotreatment of biological oilsis to reduce the overall hydrogen amount needed to convert thebiological oil to renewable diesel or to renewable base oil.

EP 1 741 768 (to Neste Oyj) provides a solution to the undesired sidereactions in the manufacture of diesel starting from a biological oilhaving more than 5 wt % free fatty acids. It was found that diluting thefree fatty acid containing feed with a large amount of hydrocarbondiluting agent reduced the undesired side reactions, allowing forimproved catalyst life time and thus more time on-stream.

There is a desire to use renewable oils that cannot be used for humanconsumption. The biological oils used for processing into renewablediesel and renewable base oils continues to become more and moredegraded as well as more complex compared to examples of puretriglyceride feeds sometimes given in the prior art. Accordingly, thereis a need in the art for processes that can utilise such degraded andcomplex biological oils or mixtures thereof that contain varying amountsof free fatty acids, in particular for the preparation of renewablediesel and renewable base oil.

WO 2007/068795 A1 (to Neste Oil Oyj) describes (see e.g. FIG. 1 of thatapplication) a complex feed which is diluted with hydrocarbons andprocessed by prehydrogenation, ketonisation, hydrodeoxygenation,stripping, hydroisomerisation, optional hydrofinishing, and distillationinto a renewable base oil, renewable diesel as well as a renewablegasoline.

There is still a need for further processes that can process low-valuebiological oils containing free fatty acids and fatty acid esters intorenewable base oils and renewable diesel in an manner that is efficientwith regards to e.g. catalyst life time and hydrogen consumption.

SUMMARY OF THE INVENTION

The present invention was made in view of the prior art described above,and the object of the present invention is to provide a more efficientprocessing method of renewable oils having a certain amount of freefatty acids, in particular, but not limited to lower hydrogenconsumption and/or increased catalyst life time.

To solve the problem, the present invention provides a method forproducing a renewable base oil and a diesel fuel from a feedstock ofbiological origin, the method comprising: a) providing a feedstock, thefeedstock comprising 2-95 wt % of a mixture of free fatty acids; 5-98 wt% fatty acid glycerols selected from mono-glycerides, di-glycerides andtri-glycerides of fatty acids; 0-50 wt % of one or more compoundsselected from the list consisting of: fatty acid esters of thenon-glycerol type, fatty amides, and fatty alcohols; the major part ofthe feedstock being the mixture of free fatty acids and fatty acidglycerols; b) separating the feedstock into at least: a free fatty acidfeed having a higher concentration of free fatty acids than thefeedstock, the free fatty acids comprising C₁₀-C₂₄ fatty acids,preferably C₁₄-C₂₂, such as C₁₄, C₁₆, C₁₈, C₂₀ and C₂₂ fatty acids; andone or more free fatty acid depleted feed(s) having higher concentrationof the compounds selected from mono-glycerides, di-glycerides andtri-glycerides of fatty acids, and having a higher boiling point thanthe free fatty acid feed; c) subjecting the fatty acid feed toketonisation reaction conditions where two fatty acids react to yield aketone stream, the ketone stream comprising as the major part(saturated) ketones; d) subjecting the ketone stream to bothhydrodeoxygenation reaction conditions and to hydroisomerisationreaction conditions, simultaneously or in sequence, to yield adeoxygenated and isomerised base oil stream comprising the renewablebase oil; e) optionally distilling the product of step d) to obtain adistilled renewable base oil; f) where the one or more free fatty aciddepleted feed(s) is transformed into a diesel product, preferably bysubjecting the one or more free fatty acid depleted feed(s) to bothhydrodeoxygenation reaction conditions and to hydroisomerisationreaction conditions, simultaneously or in sequence, to yield adeoxygenated and isomerised diesel stream comprising the diesel fuel;optionally distilling the stream obtained from step f) to obtain adistilled diesel fuel.

That is, the inventors of the present invention in a first aspect of theinvention found that degraded low-value biological oils containing freefatty acids and fatty acid esters can be processed into a renewable baseoil and a renewable diesel oil in an efficient manner by firstseparating at least part of the free fatty acids from the feedstock andthen processing this free acid feed separately in a ketonisationreaction followed by hydrodeoxygenation and hydroisomerisation reactionsto yield a renewable base oil stream. The remaining free fatty aciddepleted feed is processed in a separate hydrodeoxygenation andhydroisomerisation step to yield a renewable diesel fuel stream.

Separating the feedstock into two separate streams provides surprisingadvantages compared to a combined treatment of the entire feedstock, inthat the ketonisation reaction of the separated feed having mainly freefatty acids may be run under conditions that result in almost complete(>90%, >95%, >99% or even ≥99.5%) conversion of the free fatty acidsinto ketones, as there is less undesired oligomerisation reactioncompared to ketonisation of the entire stream. Furthermore, this ketonestream may be converted under milder hydrodeoxygenation conditions intothe corresponding paraffin, compared to a feed that also compriseunconverted fatty acids or triglycerides.

As an additional advantage, the fatty acid depleted feed will containless of the free fatty acids compared to the (initial) feedstock andtherefore use less hydrogen compared to the hydrogenation of the entirefeedstock. This results in less overall hydrogen consumption due to theketonisation reaction of the separate free fatty acid feed, becauseduring ketonisation, 75% of the oxygen content of the fatty acids isremoved as CO₂ and H₂O without consuming hydrogen, and consequently thatless hydrogen is required to convert the ketone stream. Accordingly, theseparation of the feed results in less overall hydrogen consumption,milder hydrodeoxygenation conditions for the ketone stream, whencomplete ketonisation conversion can be achieved, i.e. no unconvertedfatty acids which needs more severe reaction conditions. Fatty acids arealso very corrosive and might produce side reactions during HDO.Therefore a longer time on-stream for the reactor comprising thehydrodeoxygenation catalyst can be achieved, because it is exposed toless of the free fatty acids compared to a hydrotreatment of the samefeed that has not undergone any prior separation.

The process may additionally be for producing a naphtha fuel, where thenaphtha fuel is obtained from distillation of both the deoxygenated andisomerised base oil stream of step d) and from the distillation of thedeoxygenated and isomerised diesel stream of step f).

Prior to step a) of the method, an initial feedstock comprising fattyacid esters may be pre-treated in at least a hydrolysis step therebyproducing the feedstock, where the ratio of free fatty acids to fattyacid esters has been increased compared to the initial feedstock.

In certain variants, no pre-treatment by hydrogenation or by hydrolysismay be done in or in-between steps a)-c).

When the hydrodeoxygenation and hydroisomerisation of step d) takesplace in sequence, there may be in-between the hydrodeoxygenation andhydroisomerisation steps a stripping step, where gasses are separatedfrom liquids. This may occur in a high temperature and high pressureseparation step, for example at a temperature between 300-330° C. andpressure between 40-50 barg.

Between steps d) and e) of the method, there may be a stripping step,where gasses are separated from liquids. This may be done at atemperature between 320-350° C. and pressure between 3-6 barg.

The major part of the free fatty acid feed may be saturated free fattyacids. The major part of the free fatty acid feed may be C₁₆ fattyacids. The feedstock may be palm oil fatty acid distillate (PFAD).

The ketonisation reaction conditions may comprise one or more of thefollowing: a temperature in the range from 300 to 400° C.; a pressure inthe range from 5 to 30 barg; a WHSV in the range from 0.25-3 h⁻¹. Theketonisation reaction may be in the presence of a ketonisation catalyst,the ketonisation catalyst comprising a metal oxide catalyst. Theketonisation reaction may be in the presence of a gas in the range from0.1-1.5 gas/feed ratio (w/w), the gas being selected from one or moreof: CO₂, H₂, N₂, CH₄, H₂O.

The ketonisation reaction conditions may be selected such as to ensureliquid phase ketonisation.

The ketonisation catalyst may be a metal oxide catalyst selected fromthe list consisting of one or more of: Ti, Mn, Mg, Ca, and Zr containingmetal oxide catalyst.

The ketonisation catalyst may be TiO₂, optionally on a support. Forexample TiO₂ in anatase form having an average pore diameter of 80-160Å, and/or a BET area of 40-140 m²/g, and/or porosity of 0.1-0.3 cm³/g.

The hydrodeoxygenation reaction conditions may comprise one or more ofthe following: a temperature in the range from 250 to 400° C.; apressure in the range from 20 to 80 barg; a WHSV in the range from 0.5-3h⁻¹; and a H₂ flow of 350-900 nl H₂/l feed. The hydrodeoxygenationreaction may be performed in the presence of a hydrodeoxygenationcatalyst, such as NiMo on an alumina support.

The isomerisation reaction conditions may comprise one or more of thefollowing: a temperature in the range from 250 to 400° C.; a pressure inthe range from 10 to 60 barg; a WHSV in the range from 0.5-3 h⁻¹; a H₂flow of 100-800 nl H₂/l feed. The hydroisomerisation reaction may be inthe presence of an isomerisation catalyst, such as a catalyst comprisinga Group VIII metal and a molecular sieve, optionally on an aluminaand/or silica support.

The hydrodeoxygenation and isomerisation catalyst may be the same, suchas for example NiW.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic overview of renewable base oil production.

FIG. 2 shows a schematic overview of renewable base oil production, withadditional shared support units for base oil and diesel production, forexample in the form of sour water stripper and recycle gas loop, as wellas optional naphtha and/or diesel production.

FIG. 3 shows a schematic overview of an integrated renewable base oil,diesel and naphtha production, with additional and optional sour waterstripper and recycle gas loop.

DETAILED DESCRIPTION OF THE INVENTION

In describing the embodiments of the invention specific terminology willbe used for the sake of clarity. However, the invention is not intendedto be limited to the specific terms so selected, and it is understoodthat each specific term includes all technical equivalents which operatein a similar manner to accomplish a similar purpose.

The object of the present invention is to provide a more efficientprocessing method of renewable oils having a certain amount of freefatty acids, in particular, but not limited to lower hydrogenconsumption and increased catalyst life time.

Provided by the present invention a method for producing a renewablebase oil and a diesel fuel from a feedstock of biological origin, themethod comprising: a) providing a feedstock, the feedstock comprising2-95 wt % of a mixture of free fatty acids; 10-98 wt % fatty acidglycerols selected from mono-glycerides, di-glycerides andtri-glycerides of fatty acids; 0-50 wt % of one or more compoundsselected from the list consisting of: fatty acid esters of thenon-glycerol type, fatty amides, and fatty alcohols; the major part ofthe feedstock being the mixture of free fatty acids and fatty acidglycerols; b) separating the feedstock into at least: a free fatty acidfeed having a higher concentration of free fatty acids than thefeedstock, the free fatty acids comprising C₁₀-C₂₄ fatty acids,preferably C₁₄-C₂₂, such as C₁₄, C₁₆, C₁₈, C₂₀ and C₂₂ fatty acids; andone or more free fatty acid depleted feed(s) having higher concentrationof the compounds selected from mono-glycerides, di-glycerides andtri-glycerides of fatty acids, and having a higher boiling point thanthe free fatty acid feed; c) subjecting the fatty acid feed toketonisation reaction conditions where two fatty acids react to yield aketone stream, the ketone stream comprising as the major part ketones;d) subjecting the ketone stream to both hydrodeoxygenation reactionconditions and to hydroisomerisation reaction conditions, simultaneouslyor in sequence, to yield a deoxygenated and isomerised base oil streamcomprising the renewable base oil; e) optionally distilling the productof step d) to obtain a distilled renewable base oil; f) where the one ormore free fatty acid depleted feed(s) is transformed into a dieselproduct, preferably by subjecting the one or more free fatty aciddepleted feed(s) to both hydrodeoxygenation reaction conditions and tohydroisomerisation reaction conditions, simultaneously or in sequence,to yield a deoxygenated and isomerised diesel stream comprising thediesel fuel; optionally distilling the stream obtained from step f) toobtain a distilled diesel fuel.

That is, the inventors of the present invention in a first aspect of theinvention found that degraded low-value biological oils containing freefatty acids and fatty acid esters can be processed into a renewable baseoil and a renewable diesel oil in an efficient manner by firstseparating at least part of the free fatty acids from the feedstock andthen processing this free acid feed separately in a ketonisationreaction followed by hydrodeoxygenation and hydroisomerisation reactionsto yield a renewable base oil stream.

The remaining free fatty acid depleted feed is processed in a separatehydrodeoxygenation and hydroisomerisation step to yield a renewablediesel stream. Separating the feedstock into two separate streamsprovides surprising advantages compared to a combined treatment of theentire feedstock, in that the ketonisation reaction of the separatedfeed having mainly free fatty acids may be run under conditions thatresult in almost complete (>90%, >95%, >99% or even ≥99.5%) conversionof the free fatty acids into ketones, as there is less undesiredoligomerisation reaction compared to ketonisation of the entire stream.Furthermore, this ketone stream may be converted under milderhydrodeoxygenation conditions into the corresponding paraffin, comparedto a feed that also comprise triglycerides.

As an additional advantage, the fatty acid depleted feed will containless of the free fatty acids compared to the (initial) feedstock andtherefore use less hydrogen compared to the hydrogenation of the entirefeedstock. This results in less overall hydrogen consumption due to theketonisation reaction of the separate free fatty acid feed, becauseduring ketonisation, 75% of the oxygen content of the fatty acids isremoved as CO₂ and H₂O without consuming hydrogen, and consequently thatless hydrogen is required to convert the ketone stream. Accordingly, theseparation of the feed results in less overall hydrogen consumption,milder hydrodeoxygenation conditions for the ketone stream, i.e. moreenergy efficient, as well as a longer time on-stream for the reactorcomprising the hydrodeoxygenation catalyst, because it is exposed toless of the free fatty acids compared to a hydrotreatment of the samefeed that has not undergone any prior separation.

The method for producing a renewable base oil and a diesel fuel from afeedstock of biological origin, of the present invention will now beexplained in more details.

The renewable base oil according to the present invention may be highlyparaffinic in that it is derived from ketonisation of fatty acids.Accordingly, the renewable base oil may comprise very little aromaticsor oxygenates. Being a base oil, it boils within a base oil boilingrange, such as above 380° C.

Renewable base oil in the context of the present invention is to beunderstood as a base oil being obtained from one or more renewablesources. Base oil is a well-known term, and base oil in the context ofthe present invention is can be defined as a hydrocarbon basedcomposition with a viscosity index above 80, for example the base oil inthe context of the present invention can be even further defined asfulfilling the requirements of the API base oil groups I, II or III,preferably API group III.

The base oil affects many parameters of their end products orapplication such as the viscosity, oxidation stability, volatility, coldflow properties such as pour point, and viscosity index.

Base oils which can be manufactured from ketones obtained according tothe present invention may fulfil the requirement of Group III of TheAmerican Petroleum Institute (API) which divides base oils into fivemain groups. Groups I to III are petroleum base oil of varyingqualities.

TABLE 1 API base stock categories Group Sulfur, wt-% Saturates, %Viscosity Index (VI) I >0.03 and/or <90 80-119 II ≤0.03 and ≥90 80-119III ≤0.03 and ≥90 ≥120 IV Synthetic poly-alpha-olefins (PAOs) V Anyother type of base oil than group I-IV

A renewable diesel fuel (or renewable diesel fuel component) is ahydrocarbon diesel product as opposed to e.g. oxygen-containingbiodiesel, which are mono-alkyl fatty acid esters of biological oils.Being a diesel fuel, it boils within a diesel boiling range, such asbetween 180 and 380° C., for example between 180° C. and 350° C. As anexample diesel fuel according to EN15940 or for example a diesel fuelcomponent for a diesel fuel according to EN 590.

Common to the renewable base oil, diesel or naphtha are that they may behighly paraffinic, in that the content of aromatics and/or oxygenates isvery low, such as below 0.5 vol %.

The renewable content may be determined from the starting materials, aswell as being determined in the products by isotopic distributioninvolving ¹⁴C, ¹³C and/or ¹²C as described in ASTM D6866. Reference ismade to WO 200/068799, which is hereby incorporated by reference. Forexample, typical ¹⁴C isotope content of the total carbon content in theproduct, which is completely of biological origin, is at least 100%.Accordingly, a renewable base oil made from a feedstock of biologicalorigin will be at least 100%.

Feedstock

A feedstock is provided. The feedstock comprises as the major part amixture of free fatty acids and fatty acid esters, such as fatty acidglycerols. This is because the ketonisation reaction requires free fattyacids and because degraded or low-value biological oils are typicallymixtures of free fatty acids and fatty acid glycerols, such astriglycerides or partial glycerides. The major part of the free fattyacids and fatty acid esters may be considered to be more than 50 wt %,such as more than 70 wt %, more than 90 wt %.

In degraded biological oil, part of the triglycerides, which can be usedas high-value edible oils have been degraded to free fatty acids andpartial glycerides, such as mono- and di-glycerides. The low-valuebiological oils may therefore have a higher amount of free fatty acidscompared to the glyceride content (combined amount of mono-, di- andtri-glycerides). For example, in the refining of crude palm oil, a palmoil stripper may be used to separate crude palm oil into high-valueedible palm oil and low-value palm oil fatty acid distillate (PFAD). Thelow-value PFAD is not fit for human consumption, and may advantageouslybe used in the methods according to the present invention.

Accordingly, the feedstock may be palm oil fatty acid distillate (PFAD),which contains as the major part free fatty acids. PFAD is one exampleof low-value biological oils containing free fatty acids and fatty acidesters, such as partial glycerides. Such degraded fats are unsuited forfood production and need to be removed during the palm oil refiningprocess before the palm oil meets the food industry's quality standards.The fatty acid composition of PFAD varies by source. It is typicallydesirable to keep the degraded free fatty acid content low in edibleoils, such as palm oil, which is for the most part comprises oftriglycerides. PFAD is a by-product that is unsuited for foodproduction. It has a higher content of free fatty acids thantriglycerides (because the palm oil triglycerides are used as the ediblepalm oil), such as a higher amount of free fatty acids compared to thefatty acid ester content.

Palm oil fatty acid distillate (PFAD) is a by-product from refiningcrude palm oil. It is a light brown semi-solid at room temperature,which melts to a brown liquid on heating. While the composition of PFADvaries, the minimum free fatty acid (FFA) content of PFAD may be 60 wt%. The contractual specifications the providers of PFAD are asked tofulfil often specifies 70 wt % or more FFA, which means that the FFAcontent is often 80 wt % or more. The FFA content may be in the range of65-95 wt %, such as between 80-90 wt %.

The PFAD also contains fatty acid glycerols selected frommono-glycerides, di-glycerides, and tri-glycerides of fatty acids. Forexample the fatty acid glycerol content may be above 2 wt % or below 20wt %, for example in the range of 2-15 wt %.

The remaining components of PFAD may be unsaponifiable matters, such astocopherol, tocotrienols, sterols, squalenes, and volatile substances.For example, the unsaponifiable matter content may be above 0.5 wt % orbelow 3 wt %, for example in the range of 0.5-2.5 wt %.

PFAD may additionally comprise trace metals, for example Cr, Ni, Cu, Fe.

Bonnie Tay Yen Ping and Mohtar Yusof published in 2009 Characteristicsand Properties of Fatty Acid Distillates from Palm Oil in Oil PalmBulletin 59, p. 5-11, which provide updated information on thecomposition of PFAD, which is incorporated herein by reference.

While one example of a feedstock of biological origin according to thepresent invention is PFAD, there are many other well-suited feedstocksof biological origin, such as other plant oils or animal fat that havecontain free fatty acids, various grades of and products from therefining of plant oil or animal fat, waste cooking oil, various gradesof and products from tall oil refining, crude tall oil (CTO), tall oil,tall oil heads, tall oil fatty acids (TOFA), yellow grease, poultry fat,fish oil or acid oil side products of for example oleochemicalsproduction.

The feedstock of biological origin may further be mixtures of a numberof different feedstocks of biological origin. For example one or morekinds of plant oils or animal fats having more free fatty acids thanfatty acid esters mixed with one or more kinds of plant oils or animalfats having less free fatty acids than fatty acid esters.

While the feedstock comprises as the major part a mixture of free fattyacids and fatty acid esters, such as fatty acid glycerols, the amountsof FFA and of fatty acid esters may vary considerably as evident fromthe many different types of the free fatty acid content and fatty acidester feedstocks and mixtures mentioned above.

For practical purposes the feedstock may comprise at least 2 wt % freefatty acids, such as at least 5 wt %. For example, some separationmethods, such as distillation, are more efficient when the mixture offree fatty acids is at least 5 wt %, such as at least 7 wt % or 10 wt %.The free fatty acid content may be below 98 wt %, such as below 95 wt %,or below 90 wt %.

For practical purposes the feedstock may comprise at least 2 wt % fattyacid esters, such as at least 5 wt %. For example, some separationmethods, such as distillation, are more efficient when the content offatty acid esters is at least 5 wt %, such as at least 7 wt % or atleast 10 wt %. The fatty acid ester content may be below 98 wt %, suchas below 95 wt %, or below 90 wt %.

For example the mixture of free fatty acids may be 2-95 wt %, forexample 5-95 wt %, such as 5-90 wt % of a mixture of free fatty acids.In some feedstocks, the free fatty acid content is rather high, such asabove 50 wt % or above 70 wt %.

For example the mixture of fatty acid glycerols selected frommono-glycerides, di-glycerides and tri-glycerides of fatty acids may be5-98 wt %, for example 5-95 wt %, such as 5-90 wt % of a mixture of freefatty acids. In some feedstocks, the free fatty acid content is ratherhigh, such as above 50 wt % or above 70 wt %.

The feedstock may for example comprise 5-90 wt % free fatty acids, 5-90wt % fatty acid glycerols, and 0-20 wt % of one or more compoundsselected from the list consisting of: fatty acid esters of thenon-glycerol type, fatty amides, and fatty alcohols, where the feedstockcomprises more than 50 wt % of free fatty acids and fatty acidglycerols, such as 70 wt % or more, for example 80 wt % or more.

It is possible to increase the fatty acid content of the feedstockthereby potentially providing more renewable base oil in the process byprior to step a) of the method, an initial feedstock comprising fattyacid esters may be pre-treated in at least a hydrolysis step, such aspartial hydrolysis, thereby producing the feedstock, where the ratio offree fatty acids to fatty acid esters has been increased compared to theinitial feedstock.

The term fatty acid is well-known to the skilled person, and have beenused to characterise a carboxylic acid consisting of a hydrocarbon chainand a terminal carboxyl group, in particular any of those carboxylicacids occurring as esters in fats and oils.

The fatty acids may be saturated and unsaturated. When desiring tomanufacture dimer products in the ketonisation reaction, it isadvantageous that the fatty acids are saturated fatty acids or have areduced amount of unsaturation because double bond oligomerisations,which may lead to tarry products, are then avoided or reduced. Forexample the major part of the free fatty acid feed may be saturated freefatty acids. Advantageously, more than 90 wt % of the free fatty acidfeed is saturated fatty acids, such as more than 95 wt % or more than 99wt %.

The saturated fatty acids may be obtained from a double-bondhydrogenation reaction of either the feedstock prior to separating itinto a free fatty acid feed and one or more free fatty acid depletedfeed(s) or double bond hydrogenation of the free fatty acid feed afterseparation. For example a prehydrogenation step may utilise ahydrogenating catalyst, for example as described below under the heading“Hydrodeoxygenation of the ketone stream”—for example NiMo on an aluminasupport, but preferably double bond hydrogenation is done with supporteda noble metal, such as Pd or Pt on Silica or carbon support, which tendsto be efficient in double bond hydrogenation. The prehydrogenation maybe conducted at a temperature below 300° C., such as below 280° C. orbelow 260° C. in order to avoid hydrodeoxygenation reactions. Theprehydrogenation may also be above 90° C., such as above 110° C. orabove 120° C. in order to be high enough to ensure sufficienthydrogenation of the double bonds. For example the temperature forprehydrogenation may be 90-300° C., such as 110-280° C., for example120-260° C. The pressure may be 10-70 barg, such as 20-60 barg, forexample 30-50 barg. The WHSV may be 0.5-3.0 h⁻¹, such as 1.0-2.5 h⁻¹,for example 1.0-2.0 h⁻¹. The H₂/oil ratio may be 100-500 nl/l, such as150-450 nl/l, for example 200-400 nl/l. Accordingly, theprehydrogenation may preferably be conducted at 90-300° C., 10-70 barg,WHSV of 0.5-3.0 h⁻¹, and H₂/oil ratio of 100-500 nl/l; more preferablyat 110−280° C., 20-60 barg, WHSV of 1.0-2.5 h⁻¹, and H₂/oil ratio of150-450 nl/l; even more preferably at 120−260° C., 30-50 barg, WHSV of1.0-2.0 h⁻¹, and H₂/oil ratio of 200-400 nl/l.

The saturated fatty acids may also be present in the feedstock itself,and separation may further improve the part of free fatty acids that aresaturated. For example PFAD typically contains around 30-40 wt % C₁₆saturated fatty acids together with around 50 wt % C₁₈ saturated andunsaturated fatty acids, and less than 5 wt % fatty acids below C₁₄.This makes PFAD or PFAD containing mixtures advantageous feedstocksbecause the large amount of C₁₆ saturated fatty acids can be separatedfrom the remaining feedstock, thereby obtaining a free fatty acid feedhaving a higher amount of free fatty acids, in particular having ahigher amount of saturated free fatty acids, which are advantageous whenwanting to manufacture dimer products in the ketonisation reaction.

Separation of the Feedstock

The method involves a step b) of separating the feedstock into at least:a free fatty acid feed having a higher concentration of free fatty acidsthan the feedstock.

The separation step may for example be distillation, but other methods,such as crystallisation by cooling or a combination of distillation andcrystallisation, may be used.

The separation may for example be distillation, such as at a temperaturebetween 100° C. to 300° C. and at a distillation pressure of 0.5 kPa to5 kPa.

The free fatty acids of the free fatty acid feed may be C₁₀-C₂₄ fattyacids, preferably C₁₄-C₂₂, such as one or more of C₁₄, C₁₆, C₁₈, C₂₀ andC₂₂ fatty acids

The one or more free fatty acid depleted feed(s) has a higherconcentration of the compounds selected from mono-glycerides,di-glycerides and tri-glycerides of fatty acids compared to thefeedstock of biological origin. For example, the one or more free fattyacid depleted feed(s) may have a concentration that is at least 5%higher, such as at least 25% higher, of the compounds selected frommono-glycerides, di-glycerides and tri-glycerides of fatty acidscompared to the feedstock of biological origin. For example, the one ormore free fatty acid depleted feed(s) may have a content of free fattyacids that is below 2 wt %.

For example, the free fatty acid feed may have a concentration that isat least 5% higher, such as at least 25% higher, of the compoundsselected from mono-glycerides, di-glycerides and tri-glycerides of fattyacids compared to the feedstock of biological origin. For example, thefree fatty acid feed may have a content of fatty acid glycerols selectedfrom mono-glycerides, di-glycerides and tri-glycerides of fatty acidsthat is below 5 wt %.

The one or more free fatty acid depleted feed(s) may have a higherboiling point than the free fatty acid feed and/or have a higher averagemolecular weight. For example the higher boiling point can be a higherfinal boiling point compared to the free fatty acid feed and the higheraverage molecular weight can be measured as a weighted average. Theboiling points may for example be measured using SimDist GC boilingpoint plots according to ASTM D 2887.

The feedstock usually contains both C₁₆ and C₁₈ fatty acids, which maybe separated by distillation for example, and the major part of the freefatty acid feed may be C₁₆ fatty acids.

Ketonisation

The fatty acid feed that has been separated from the feedstock is instep c) subjected to ketonisation reaction conditions where two fattyacids react to yield a ketone stream, the ketone stream comprising asthe major part ketones.

The ketonisation reaction yields both water and carbon dioxide, whichmay be separated from the oil fraction, for example water may beseparated by decanting, and carbon dioxide and other gaseous componentsmay be separated in a flash drum.

The ketonisation reaction conditions may comprise one or more of thefollowing: a temperature in the range from 300 to 400° C.; a pressure inthe range from 5 to 30 barg; a WHSV in the range from 0.25-3 h⁻¹.

For example the ketonisation reaction conditions may involve atemperature in the range from 300 to 400° C.; a pressure in the rangefrom 5 to 30 barg; a WHSV in the range from 0.25-3 h⁻¹. Preferably theketonisation reaction conditions may involve a temperature in the rangefrom 330 to 370° C.; a pressure in the range from 10 to 25 barg; a WHSVin the range from 0.5-2 h⁻¹. More preferably the ketonisation reactionconditions may involve a temperature in the range from 340 to 360° C.; apressure in the range from 15 to 20 barg; a WHSV in the range from1.0-1.5 h⁻¹.

The ketonisation reaction is usually conducted in the presence of aketonisation catalyst, the ketonisation catalyst comprising a metaloxide catalyst. For example, the ketonisation catalyst may be a metaloxide catalyst selected from the list consisting of one or more of: Ti,Mn, Mg, Ca, and Zr containing metal oxide catalyst. For example, theketonisation catalyst may be TiO₂, such as for example TiO₂ in anataseform having an average pore diameter of 80-160 Å, and a BET area of40-140 m²/g, and porosity of 0.1-0.3 cm³/g.

The ketonisation reaction may be pressurised by a gas. For example theketonisation may be conducted in the presence of a gas in the range from0.1-1.5 gas/feed ratio (w/w), the gas being selected from one or moreof: CO₂, H₂, N₂, CH₄, H₂O. The gas used for pressurisation mayadvantageously be CO₂ as it is produced as a by-product of theketonisation reaction and can be recycled as a pressurisation gas.

The ketonisation reaction conditions may be selected such as to ensureliquid phase ketonisation or at least that the feed introduction to theketonisation step is in liquid form. By ensuring liquid phaseketonisation, by suitable selection of a combination of catalyst,pressure and temperature, the reaction results in less undesiredby-products, compared to gas phase ketonisation. Gas phase ketonisationnormally needs high gas recycle in order to transfer fatty acids fromsolid/liquid form to gas phase, due to the high boiling points of fattyacids. This means that the reactor system for the gas phase ketonisationmust be bigger and more complex; this will increase the investment costssignificantly.

The ketone stream comprises dimers of the free fatty acid feed. Forexample, if the free fatty acid feed is exclusively palmitic acid (C16:0fatty acid), then the ketone stream will produce a C₃₁ ketone, and ifthe free fatty acid feed is a mixture of C₁₆ and C₁₈ fatty acids, thenthe ketone stream will produce a mixture of C₃₁, C₃₃, and C₃₅ ketones.

As mentioned above, the free fatty acid stream may be a saturated freefatty acid feed. This reduces the amount of unwanted oligomerisationproduct. If the free fatty acid feed contains unsaturated free fattyacids, these free fatty acids may be saturated by hydrogenation. Such aprehydrogenation step is usually conducted under mild conditions in thepresence of a hydrogenation catalyst at temperatures between 50 and 400°C., under a hydrogen pressure ranging from 0.1 to 20 MPa, preferably attemperatures between 150 and 300° C., under a hydrogen pressure rangingfrom 1 to 10 MPa. The prehydrogenation catalyst contains metals of theGroup VIII and/or VIA of the periodic system of the elements. Theprehydrogenation catalyst is preferably a supported Pd, Pt, Rh, Ru, Ni,Cu, CuCr, NiMo or CoMo catalyst, the support being activated carbon,alumina and/or silica.

However, it is desirable that no hydrogenation of free fatty acids isdone. In particular the palmitic acid (saturated free fatty acid) inPFAD may be separated by distillation, thus yielding a saturated freefatty acid feed of palmitic acid without any hydrogenation necessary.

Accordingly, in certain variants of the present invention, nopre-treatment by hydrogenation or by hydrolysis is done in or in-betweensteps a)-c).

The ketonisation reaction of the free fatty acid feed may be run underconditions that result in almost complete (>90%, >95%, >99% or even≥99.5%) conversion of the free fatty acids into ketones, as there isless undesired oligomerisation reaction compared to ketonisation of theentire stream. This provides distinct advantages downstream in thathydrodeoxygenation of the ketone stream requires less severehydrodeoxygenation conditions in order to ensure complete deoxygenationof the ketone feed, compared to e.g. the free fatty acid depleted feed,which may contain both free fatty acids and fatty acid glycerols. Lesssevere conditions, for example lower reaction temperature in thehydrodeoxygenation step results in less energy used, a reduction inundesirable side reactions, such as coking, leading to a longer catalystlife time.

Hydrodeoxygenation of the Ketone Stream

The ketone stream obtained from the ketonisation reaction may beisolated by decanting the water from the oil and separating the gaseousproducts from the liquid products, for example in a flash drum. Theketone stream is then in step d) subjected to both hydrodeoxygenationreaction conditions and to hydroisomerisation reaction conditions.

The hydrodeoxygenation and hydroisomerisation reaction conditions mayeither be done simultaneously or in sequence. The product is adeoxygenated and isomerised base oil stream comprising the renewablebase oil.

The hydrodeoxygenation reaction may be performed in the presence of ahydrodeoxygenation catalyst, such as CoMo, NiMo, NiW, CoNiMo on asupport, for example an alumina support. The hydrodeoxygenation catalystmay be typical hydrodeoxygenation catalysts in the art, for example itmay comprise a hydrogenation metal on a support, such as for example acatalyst selected from a group consisting of Pd, Pt, Ni, Co, Mo, Ru, Rh,W or any combination of these. The hydrodeoxygenation step is done underhydrodeoxygenation conditions to provide the base oil product. Thehydrodeoxygenation step may for example be conducted at a temperature of250-400° C. and at a pressure of 20-80 barg. The hydrotreatment step mayfor example be conducted at a temperature of 250-400° C., at a pressureof between 20 and 80 barg, a WHSV of 0.5-3 h⁻¹, and a H₂/oil ratio of350-900 nl/l.

As mentioned above, the hydrodeoxygenation reaction conditions maycomprise: a temperature in the range from 250 to 400° C.; a pressure inthe range from 20 to 80 barg; a WHSV in the range from 0.5-3 h⁻¹; and aH₂ flow of 350-900 nl H₂/l feed. The catalyst may be NiMo on aluminasupport.

Preferably, the hydrodeoxygenation condition may involve a temperaturein the range from 280 to 350° C.; a pressure in the range from 30 to 60barg; a WHSV in the range from 1.0-2.5 h⁻¹; and a H₂ flow of 350-750 nlH₂/l feed. The catalyst may be NiMo on alumina support.

More preferably, the hydrodeoxygenation condition may involve atemperature in the range from 300 to 330° C.; a pressure in the rangefrom 40 to 50 barg; a WHSV in the range from 1.0-2.0 h⁻¹; and a H₂ flowof 350-500 nl H₂/l feed. The catalyst may be NiMo on alumina support.

Further in the process, the ketone stream may be diluted with a streamof hydrocarbons. The dilution may be 30 wt % hydrocarbons and 70 wt %ketone stream, for example between 30-85 wt % hydrocarbon and 15-70 wt %ketone stream. The stream of hydrocarbons used for dilution may in partor fully be product recycle.

The product recycle may have undergone fractionation before beingrecycled, for example it may be the fraction boiling above 380° C. thatis recycled or any other fraction of the base oil mixture describedherein.

As mentioned above hydrodeoxygenation catalyst may for example be amolybdenum or wolfram catalyst, typically on a support, such as Al₂O₃.The catalyst may or may not be promoted. Typical promoters are Ni and/orCo. Promoted hydrodeoxygenation catalysts may for example be NiMo, CoMo,NiW, CoW, NiCoMo. When a wolfram based catalyst is used, such as a NiW,or a Pd or Pt catalyst it has the further advantage that it can alsocatalyse isomerisation reactions, thus enabling a simultaneoushydrodeoxygenation and hydrosiomerisation reaction. Accordingly, thehydrodeoxygenation and isomerisation catalyst may be the same, such asfor example NiW, or a Pt catalyst, such as Pt/SAPO in mixture with apromoted Mo catalyst on a support, e.g. NiMo on alumina.

The hydrodeoxygenation is done in the presence of hydrogen gas in ahydrodeoxygenation zone, which may be a catalyst bed in a fixed bedreactor.

When the hydrodeoxygenation and hydroisomerisation of step d) takesplace in sequence, in-between the hydrodeoxygenation andhydroisomerisation there may be a stripping step, where gasses areseparated from liquids. This may occur in a high temperature and highpressure separation step, for example at a temperature between 300-330°C. and pressure between 40-50 barg.

Hydroisomerisation of the Ketone Stream

The product of the hydrodeoxygenation step is subjected to anisomerization step in the presence of hydrogen and an isomerizationcatalyst. Both the hydrotreatment step and isomerisation step may beconducted in the same reactor, and even in the same reactor bed. Theisomerisation catalyst may be a noble metal bifunctional catalyst suchas a Pt containing commercial catalyst, for example Pt-SAPO orPt-ZSM-catalyst or for example a non-noble catalyst, such as NiW. Thehydrodeoxygenation and hydroisomerisation steps may be done in the samecatalyst bed using e.g. the NiW catalyst in both the hydrotreatment andisomerisation step. The NiW catalyst may additionally result in morehydrocracking to diesel and naphtha products, and may be an advantageouscatalyst if such products are also desired together with the renewablebase oil product. The isomerization step may for example be conducted ata temperature of 250-400° C. and at a pressure of 10-60 barg. Asexplained elsewhere in this description, it is desirable to reduce theseverity of the isomerisation reaction to avoid or reduce the amount ofcracking of the renewable base oil product. The isomerisation step mayfor example be conducted at a temperature of 250-400° C., at a pressureof between 10 and 60 barg, a WHSV of 0.5-3 h⁻¹, and a H₂/oil ratio of100-800 nl/l.

The hydrodeoxygenation and hydroisomerisation reactions may be done insequence. The sequence is typically hydrodeoxygenation followed byhydroisomerisation, but this sequence may also be reversed. Theisomerisation reaction conditions may comprise one or more of thefollowing: a temperature in the range from 250 to 400° C.; a pressure inthe range from 10 to 60 barg; a WHSV in the range from 0.5-3 h⁻¹; a H₂flow of 100-800 nl H₂/l feed.

Preferably the isomerisation reaction conditions comprise a temperaturein the range from 280 to 370° C.; a pressure in the range from 20 to 50barg; a WHSV in the range from 0.5-2.0 h⁻¹; a H₂ flow of 200-650 nl H₂/lfeed.

More preferably the isomerisation reaction conditions comprise atemperature in the range from 300 to 350° C.; a pressure in the rangefrom 25 to 45 barg; a WHSV in the range from 0.5-1.0 h⁻¹; a H₂ flow of300-500 nl H₂/l feed.

The hydroisomerisation reaction may be in the presence of anisomerisation catalyst, such as a catalyst comprising a Group VIIImetal, preferably Pt, and a molecular sieve, optionally on support. Thesupport may for example be selected from silica, alumina, clays,titanium oxide, boron oxide, zirconia, which can be used alone or as amixture, preferably silica and/or alumina. The molecular sieve may forexample be zeolites, such as ZSM or aluminophosphate molecular sieves,such as SAPO, such as SAPO-11, MeAPO, MeAPSO, where Me is e.g. Fe, Mg,Mn, Co or Zn, or other elements (EI) molecular sieves EIAPO or EIAPSO,e.g. silica-alumina, Y zeolite, SAPO-11, SAPO-41, ZSM-22, ferrierite,ZSM-23, ZSM-48, ZBM-30, IZM-1, COK-7. Suitable molecular sieves andcharacteristics of molecular sieves suitable for hydroisomerisationapplications are known to the skilled person and have been described inthe literature, such as in Handbook of heterogeneous catalysis from VCHVerlagsgesellschaft mbH with editiors Ertl, KnÖzinger and Weitkamp,volume 4, pages 2036-2037, which is hereby incorporated by referenceherein.

Purifying the Base Oil

Between steps d) and e) of the method, there may be a stripping step,where gasses are separated from liquids. This may be done at atemperature between 320-350° C. and pressure between 3-6 barg.

Between steps d) and e) of the method, and preferably after thestripping step if present, there may also be an optional hydrofinishingstep, where the product are stabilised by conducting a furtherhydrogenation step in the presence of a hydrogenating catalyst, forexample as described above under the heading “Hydrodeoxygenation of theketone stream”, for example NiMo on an alumina support. However, otherhydrofinishing catalysts containing metals of the Group VIII of theperiodic system of the elements on e.g. an alumina and/or silica supportmay also be used. The hydrofinishing catalyst is preferably a supportedPd, Pt, or Ni catalyst, the support being alumina and/or silica.

The hydrofinishing step is similar to the prehydrogenation step withregards to the reaction conditions. However, in the hydrofinishing step,typically higher pressures, and to some extent higher temperatures areutilised. This is because the feed is fully deoxygenated at this stagecompared to a potential prehydrogenation step. The hydrofinishing stepis present in order to stabilise the product which among other thingsinvolves hydrogenation of double bonds or aromatic compounds that ispresent or has formed during the previous steps, such as duringhydroisomerisation. The hydrofinishing step may be conducted at atemperature below 300° C., such as below 280° C. or below 260° C. Thehydrofinishing may also be above 180° C., such as above 190° C. or above200° C. For example the temperature for prehydrogenation may be 180-300°C., such as 190-280° C., for example 200-250° C. The pressure may be100-200 barg, such as 120-180 barg, for example 140-160 barg. The WHSVmay be 0.5-3.0 h⁻¹, such as 0.75-2.5 h⁻¹, for example 1.0-2.0 h⁻¹. TheH₂/oil ratio may be 100-500 nl/l, such as 150-450 nl/l, for example200-400 nl/l. Accordingly, the prehydrogenation may preferably beconducted at 90-300° C., 10-70 barg, WHSV of 0.5-3.0 h⁻¹, and H₂/oilratio of 100-500 nl/l; more preferably at 110-280° C., 20-60 barg, WHSVof 1.0-2.5 h⁻¹, and H₂/oil ratio of 150-450 nl/l; even more preferablyat 120-260° C., 30-50 barg, WHSV of 1.0-2.0 h⁻¹, and H₂/oil ratio of200-400 nl/l.

The deoxygenated and isomerised base oil stream obtained in step d)comprises the renewable base oil. It may optionally in a step e) bedistilled to obtain a distilled renewable base oil; for example thedeoxygenated and isomerised base oil stream may be distilled to obtainthe renewable base oil in a fraction having a boiling point of more than380° C., such as more than 450° C., for example more 460° C. or more,such as 470° C. or more, such as 480° C. or more, or for example 500° C.or more. For example the distillation may yield one or more fractions ofrenewable base oils, for example above 380° C., for example a fractionbetween 380-450° C. and a fraction above 450° C.

During distillation other fractions, such as a naphtha fraction and/or adiesel fraction may also be isolated. These fractions are the result ofcracking during the hydrodeoxygenation and hydroisomerisation reactions,as well as a very little amount of unconverted free fatty acid from theketonisation step.

Hydrodeoxygenation and Isomerisation of the FFA Depleted Feed(s)

The one or more free fatty acid depleted feed(s) may be transformed intoa middle distillate product, such as a diesel product, preferably in astep f) by being subjected to both hydrodeoxygenation reactionconditions and to hydroisomerisation reaction conditions, simultaneouslyor in sequence, to yield a deoxygenated and isomerised diesel streamcomprising the diesel fuel; optionally distilling the stream obtainedfrom step f) to obtain a distilled diesel fuel.

This may be done in the same manner as described under the heading“Hydrodeoxygenation and isomerisation of the ketone stream”. The one ormore free fatty acid depleted feed(s) may also be diluted with a streamof hydrocarbons before the hydrodeoxygenation and hydroisomerisation.The dilution may be 30 wt % hydrocarbons and 70 wt % stream, for examplebetween 30-85 wt % hydrocarbon (diluent) and 15-70 wt % free fatty aciddepleted feed (fresh feed). The dilution may also be high for example3:1 and up to 20:1, for example 4:1 and up to 20:1, such as 5:1 and upto 20:1 (hydrocarbons:fresh feed) The stream of hydrocarbons used fordilution may in part or fully be product recycle.

The product recycle may have undergone fractionation before beingrecycled, for example it may be the fraction boiling in the diesel rangeof around 180-350° C., such as 210-380° C. that is recycled.

Renewable Base Oil, Diesel and Naphtha

The method according to the present invention produces renewable baseoil and renewable diesel. In the course of production the renewable baseoil will also comprise small amounts of renewable diesel and naphtha asexplained above. The deoxygenated and isomerised diesel stream comprisesin addition to the renewable diesel fuel small amounts of renewablenaphtha, which can be separated and pooled with the renewable naphthafrom the renewable base oil fractionation, and the renewable dieselobtained from distillation of the deoxygenated and isomerised dieselstream can be pooled with the renewable diesel from the renewable baseoil fractionation.

Accordingly, the process may additionally be for producing a naphthafuel, where the naphtha fuel is obtained from distillation of both thedeoxygenated and isomerised base oil stream of step d) and from thedistillation of the deoxygenated and isomerised diesel stream of stepf).

For example the combined amounts of renewable naphtha, diesel and baseoil obtained from the feedstock of biological origin may be between 5-95wt % renewable base oil, 5-95 wt % diesel, and 0-30 wt % naphtha; forexample between 5-95 wt % renewable base oil, 5-95 wt % diesel, and 5-30wt % naphtha.

The Invention Will Now be Described with Reference to the Figures.

FIG. 1 describes a method for producing a renewable base oil from afeedstock of biological origin denoted “PFAD”. While the feedstock ofbiological origin in FIG. 1 has been denoted PFAD, the method in FIG. 1is not limited to PFAD, but may be any feedstock of biological origin asdescribed herein.

The method comprises a step a) of providing the feedstock of biologicalorigin as described herein, in particular under the heading “Feedstock”above. The feedstock of biological origin denoted “PFAD” is then in astep b) separated into at least a free fatty acid feed by distillationdenoted “FFA distillation”, where a distillate having a higherconcentration of free fatty acids than the feedstock is obtained.Reference is made to the section above titled “Separation of thefeedstock”. The free fatty acid feed obtained from the “FFAdistillation” is then in a step c) subjected to ketonisation reactionconditions (denoted “Ketonisation”) where two fatty acids react to yielda ketone stream, the ketone stream comprising as the major part ketones.Reference is made to the section above titled “Ketonisation” foradditional details about the ketonisation step.

The ketone stream is then in a step d) subjected to hydrodeoxygenationreaction conditions, denoted “HDO”, where hydrogen is also supplied.When the hydrodeoxygenation and hydroisomerisation steps take place insequence rather than simultaneously, the deoxygenated base oil streammay be stripped of water and gasses in a stripping step, denoted“intermediate stripper”. The HDO step may be as described above underthe heading “Hydrodeoxygenation of the ketone stream”, and the strippingstep may be as described above under the heading “Purifying the baseoil”. The deoxygenated base oil may then be subjected tohydroisomerisation reaction conditions, denoted “Isomerisation”, wherehydrogen is also supplied, yielding a deoxygenated and isomerised baseoil stream comprising the renewable base oil. The hydroisomerisationconditions may be as described above under the heading“Hydroisomerisation of the ketone stream”. When the hydrodeoxygenationand hydroisomerisation step takes place simultaneously, as for exampleas described under the heading “Hydroisomerisation of the ketonestream”, then the “HDO” and “Isomerisation” are one and same reactor,and the “intermediate stripper” is placed downstream of the simultaneoushydrodeoxygenation and hydroisomerisation. The deoxygenated andisomerised base oil stream may optionally be stabilised denoted “Productstabilization”, for example as disclosed above under the heading“Purifying the base oil”.

The method also comprises a step e) of distilling the product of step d)to obtain a distilled renewable base oil, typically under vacuum,denoted “Vacuum distillation”, for example as disclosed above under theheading “Purifying the base oil”. The distillation may yield one or morefractions of renewable base oils, collectively denoted “RBO”, forexample above 380° C., for example a fraction between 380-450° C. and anfraction above 450° C.

By-products from the product stabilization and fractions other than theRBO fractions from the vacuum distillation may be directed as streams tofuel production denoted “Stream to fuel production”, for example for theproduction of one or more fractions in the naphtha boiling range, suchas below 180° C. and diesel boiling range, 180-350° C., for example asdescribed above under the heading “Renewable base oil, diesel andnaphtha”.

FIG. 2, describes in addition to the “PFAD”, “FFA distillation”,“Ketonisation”, “HDO”, “intermediate stripper”, “Isomerisation”,“Product stabilization”, “Vacuum distillation”, and “RBO” of FIG. 1,three elements, which can be used together with the method either aloneor in combination.

The first element is shared support units for base oil and dieselproduction (“Shared support units for baseoil and diesel production”),which may involve the removal of water formed during the ketonisationreaction and the hydrodeoxygenation by stripping or decantation (forexample in the form of a sour water stripper denoted “Sour waterstripper” in FIG. 3). The shared support units additionally provides forthe possibility of having a recycle gas loop in order to recyclehydrogen from the hydrodeoxygenation step (“HDO”) or from the dieselfuel production (“Diesel fuel production”), optionally purifying thehydrogen gas by removal of e.g. steam in a stripper before being fed tothe ketonisation step (“Ketonization”) as a pressurising gas for theketonisation reaction, as for example disclosed above under the heading“Ketonisation”.

The second element is the hydrofinishing step for saturation ofpotential aromatic compounds or double bonds present in order tostabilise the product (“Product stabilisation”), as described aboveunder the heading “Purifying the base oil”. The product stabilizationwill also stabilise the potential naphtha boiling range (“Naphtastabilization”) and diesel boiling range (“Diesel stabilization”)compounds present in the renewable base oil due to e.g. cracking duringhydroisomerisation and/or from the FFA that did not react in theketonisation reaction and was carried forward. The vacuum distillation(“Vacuum distillation”) of the renewable base oil may therefore yieldone or more fractions of renewable base oils, collectively denoted“RBO”, for example above 380° C., for example a fraction between380-450° C. and an fraction above 450° C., as well as one or morefractions in the Naphtha boiling range, such as below 180° C. and dieselboiling range, 180-350° C., for example as described above under theheading “Renewable base oil, diesel and naphtha”.

The third element is the separation step (“FFA distillation”). Theseparation of the feedstock of biological origin (“PFAD”) into a freefatty acid feed, which is processed into renewable base oil (“RBO”) viaketonisation, and a bottom stream (“Bottom stream”), which can forexample be further processed into a diesel fuel (“Diesel fuelproduction”). The separation step (“FFA distillation”) allows for a moreversatile production of renewable base oil (“RBO”), both in respect ofquality of the RBO, as well as the quantity. With regards to thequality, the FFA distillation can, as shown in example 1, produce a freefatty acid feed essentially consisting only of e.g. palmitic acid. Thissingle carbon fatty acid can then be processed via ketonisation torenewable base oil which consists essentially of C₃₁ base oil having awell-defined composition, which is an industrially relevant product forbase oil producers in that they are able to fine tune the particularproperties required of base oils.

With regards to the quantity, the separation step also provides for anRBO production that can be scaled depending on the demand of the marketfor either renewable base oil or renewable diesel; if more diesel isdemanded than base oil, the separation step can for example take a morenarrow cut of exclusively palmitic acid and produce a base oil with avery well-defined composition, whereas if less renewable diesel isdemanded by the market, the separation step can for example take a morebroad cut of the feedstock of biological origin, which may for exampleinclude both the C₁₆ and C₁₈ fatty acids, which can be processed intorenewable base oil products via ketonisation, yielding RBO mixturescomprising C₃₁, C₃₃ and C₃₅ base oils. The amount of free fatty acids ina feedstock of biological origin as defined herein (see e.g. the sectiontitled “feedstock”) may be further increased by prior to step a) of themethod, the initial feedstock comprising fatty acid esters may bepre-treated in at least a hydrolysis step thereby producing thefeedstock, where the ratio of free fatty acids to fatty acid esters hasbeen increased compared to the initial feedstock.

FIG. 3, describes in addition to FIGS. 1 and 2 that the bottom stream ofFIG. 2 is now a fatty acid depleted feed (“renewable diesel line”) forthe production of diesel in a step f) of subjecting the one or more freefatty acid depleted feed(s) (“renewable diesel line”) to an optionalprehydrogenation stage (“pretreatment”) conducted under mild conditionsin the presence of a hydrogenation catalyst, as described under theheading “Ketonisation”. The prehydrogenation is intended to saturatedouble bonds in the remaining fatty acids and fatty acid esters, whichenables the use of more severe hydrodeoxygenation conditions in thesubsequent step (“HDO”).

The HDO step may be as described above under the heading“Hydrodeoxygenation and isomerisation of the FFA depleted feed(s)”. Thewater is separated (“Sour water stripper”) in a stripper, which may beshared with the RBO line. Additionally, hydrogen may be recycled via therecycle gas loop, which may also be shared with the RBO line. Thedeoxygenated diesel stream may then be subjected to hydroisomerisationreaction conditions, denoted “Isomerisation”, where hydrogen is alsosupplied, yielding a deoxygenated and isomerised diesel streamcomprising the diesel fuel.

As mentioned above under the section “Hydrodeoxygenation andisomerisation of the FFA depleted feed(s)”, the hydrodeoxygenation andhydroisomerisation may be conducted simultaneously or in sequence. Thedeoxygenated and isomerised diesel stream may optionally be stabiliseddenoted “Diesel stabilization” and “Naphta stabilization”, for examplein the form of the hydrofinishing step as disclosed above under theheading “Purifying the base oil”. The vacuum distillation (“Vacuumdistillation”) of the a deoxygenated and isomerised diesel stream maytherefore yield one or more fractions of Diesel fuel, collectivelydenoted “Diesel”, in e.g. the boiling range, 180-350° C., as well as oneor more fractions in the Naphtha boiling range, such as below 180° C.,for example as described above under the heading “Renewable base oil,diesel and naphtha”.

When describing the embodiments of the present invention, thecombinations and permutations of all possible embodiments have not beenexplicitly described. Nevertheless, the mere fact that certain measuresare recited in mutually different dependent claims or described indifferent embodiments does not indicate that a combination of thesemeasures cannot be used to advantage. The present invention envisagesall possible combinations and permutations of the described embodiments.

The terms “comprising”, “comprise” and comprises herein are intended bythe inventors to be optionally substitutable with the terms “consistingof”, “consist of” and “consists of”, respectively, in every instance.

EXAMPLES Example 1—Separation of PFAD into a Palmitic Acid Feed and aPalmitic Acid Depleted Feed

Palm fatty acid distillate (PFAD) was separated into a palmitic acidfeed and a palmitic acid depleted feed by distillation at a temperatureof about 250-275° C. and at 0.01-0.05 bar pressure.

This resulted in a palmitic acid feed, which was 97.0 wt % pure withminor impurities of: C₁₈ fatty acids (0.42 wt %); C₁₄ fatty acids (2.5wt %).

The remaining palmitic acid depleted feed contained partial glyceridesand C₁₈ fatty acids as the primary components:

TABLE 1 Distillation of PFAD Carbon PFAD feed Distillate (wt %) Bottom(wt %) number (wt %) (Enriched feed) (depleted feed) C14:0 FFA 1.1 2.50.0 C16:0 FFA 42.4 97 0.4 C18:2 FFA 1.2 0.2 2.0 C18:1 FFA 42.1 0.2 74.4C18:0 FFA 4.5 0.01 8.0 MG 0 0 0.0 DG 2.6 0 4.6 TG 6.1 0 10.8 FFA: freefatty acids; MG, DG, TG: mono-, di-, tri-glyderides

Example 2—Ketonisation of the Palmitic Acid Feed

The palmitic acid feed was fed to a fixed bed (pilot) reactor operatedin continuous mode comprising a catalyst bed loaded with 250 g catalystmaterial (TiO₂ BET 50-54 m²/g; average pore size 100-200 Å;crystallinity 50-100%). The ketonisation was conducted in the liquidphase at a pressure of about 18 barg, temperature of about 360° C., WHSVof about 1.0 h⁻¹, and an extra gas flow of 131 l/h nitrogen. Theketonisation reaction conditions resulted in 85% fatty acid conversionthereby obtaining a ketone stream.

Example 2a—Ketonisation of the Palmitic Acid Feed

The palmitic acid feed was fed to a fixed bed reactor operated incontinuous mode comprising a catalyst bed loaded with 250 g catalystmaterial (TiO₂ BET 50-54 m²/g; average pore size 100-200 Å;crystallinity 50-100%). The ketonisation was conducted in the liquidphase at a pressure of about 25 barg, temperature of about 360° C., WHSVof about 0.5 h⁻¹, without extra gas flow. The ketonisation reactionconditions resulted in 99.9% fatty acid conversion thereby obtaining aketone stream.

Example 2b—Ketonisation of the Palmitic Acid Feed

The palmitic acid feed was fed to a fixed bed reactor operated incontinuous mode comprising a catalyst bed loaded with 20 g catalystmaterial (TiO₂ BET 50-54 m²/g; average pore size 100-200 Å;crystallinity 50-100%). The ketonisation was conducted in the liquidphase at a pressure of about 10 barg, temperature of about 360° C., WHSVof about 1.0 h⁻¹, and an extra gas flow of 5 l/h hydrogen. Theketonisation reaction conditions resulted in 99.9% fatty acid conversionthereby obtaining a ketone stream.

Example 2c—Ketonisation of the Palmitic Acid Feed

The palmitic acid feed was fed to a fixed bed reactor operated incontinuous mode comprising a catalyst bed loaded with 20 g catalystmaterial (TiO₂ BET 50-54 m²/g; average pore size 100-200 Å;crystallinity 50-100%). The ketonisation was conducted in the liquidphase at a pressure of about 10 barg, temperature of about 360° C., WHSVof about 1.0 h⁻¹, and an extra gas flow of 5 l/h carbon dioxide. Theketonisation reaction conditions resulted in 99.4% fatty acid conversionthereby obtaining a ketone stream.

Example 3—Hydrodeoxygenation and Isomerisation of the Ketone Stream

The resulting ketone stream was hydrodeoxygenated over a NiMo/Al₂O₃catalyst at a temperature of about 310° C., a pressure of about 40 bar,a WHSV of about 1.5 h⁻¹, and H₂/feed oil ratio of 900 nl/l to yield ahydrodeoxygenated product. The efficiency of oxygen removal was 99.9%for the HDO step.

The resulting hydrodeoxygenated product was hydroisomerised overPt/SAPO-11 on alumina support as the hydroisomerisation catalyst with ata temperature of about 350° C., a pressure of about 40 bar, and at aWHSV of about 1.0 h⁻¹ to yield hydroisomerised base oil product.

The hydroisomerised base oil product is fractionated into a naphthafraction (below 180° C.), a diesel fraction (180-350° C.), and the 380+°C. fraction was isolated as a renewable base oil product.

Example 3a—Hydrodeoxygenation and Isomerisation of the Ketone Stream

The resulting ketone stream was hydrodeoxygenated over a NiMo/Al₂O₃catalyst at a temperature of about 310° C., a pressure of about 40-50bar, a WHSV of about 1.5 h⁻¹, and H₂/feed oil ratio of 900 nl/l to yielda hydrodeoxygenated product. The efficiency of oxygen removal was 99.9%for the HDO step.

The resulting hydrodeoxygenated product was hydroisomerised overPt/SAPO-11 on alumina support as the hydroisomerisation catalyst with atemperature of about 348° C., a pressure of about 40 bar, at a WHSV ofabout 1.0 h⁻¹, and H₂/feed oil ratio of 800 nl/l oil to yield ahydroisomerised base oil product.

The hydroisomerised base oil product is fractionated into a naphthafraction (below 180° C.), a diesel fraction (180-350° C.), and the 380+°C. fraction was isolated as a renewable base oil product (59.9 wt %),renewable diesel (22.9 wt %), renewable naphtha boiling in the range of35-180° C. (1.3 wt %) the remainder being product gasses (11.9 wt %) andprocess oil boiling between 350-380° C. (4.0 wt %).

The renewable base oil product had the following properties: Kinematicviscosity at 40° C. of 17.7 mm²/s; Kinematic viscosity at 100° C. of 4.2mm²/s; a viscosity index (VI) of 151; cloud point of −1.1° C.; pourpoint of −17° C.; and aromatics content below 0.1 wt %. The kinematicviscosities measured using ENISO3104, Viscosity index using ASTM D 2270;cloud point using ASTM D 5771; and pour point using ASTM D 5950;aromatic compounds using ASTM D 7419.

Example 4—Hydrodeoxygenation and Isomerisation of the Remaining PalmiticAcid Depleted Stream

The remaining palmitic acid depleted feed was hydrodeoxygenated over aNiMo/Al₂O₃ catalyst at a temperature of about 310° C., a pressure ofabout 50 bar, a WHSV of about 1.0-1.5 h⁻¹, and H₂/feed oil ratio of 900nl/l to yield a hydrodeoxygenated product. The efficiency of oxygenremoval was 99.9% for the HDO step.

The resulting hydrodeoxygenated product was hydroisomerised over areduced platinum molecular sieve/Al₂O₃ as the hydroisomerisationcatalyst with at temperatures of about 300-350° C., a pressure of about20-40 bar, and at a WHSV of about 0.8-1.0 h⁻¹ to yield a hydroisomerisedbase oil product.

The hydroisomerised diesel product is fractionated into a naphthafraction (below 180° C.), a diesel fraction (180-350° C.).

1. Method for producing a renewable base oil and a diesel fuel from afeedstock of biological origin, the method comprising: a) providing afeedstock, the feedstock containing 2-95 wt % of a mixture of free fattyacids; 5-98 wt % fatty acid glycerols selected from mono-glycerides,di-glycerides and tri-glycerides of fatty acids; 0-50 wt % of one ormore compounds selected from a list consisting of: fatty acid esters ofthe non-glycerol type, fatty amides, and fatty alcohols; wherein a majorpart of the feedstock is the mixture of free fatty acids and fatty acidglycerols; b) separating the feedstock into at least: a free fatty acidfeed having a higher concentration of free fatty acids than thefeedstock, the free fatty acids containing C₁₀-C₂₄ fatty acids; and oneor more free fatty acid depleted feed(s) having higher concentration ofthe compounds selected from mono-glycerides, di-glycerides andtri-glycerides of fatty acids, and having a higher boiling point thanthe free fatty acid feed; c) subjecting the free fatty acid feed toketonisation reaction conditions where two fatty acids react to yield aketone stream, the ketone stream containing as a major part saturatedketones; and d) subjecting the ketone stream to both hydrodeoxygenationreaction conditions and to hydroisomerisation reaction conditions,simultaneously or in sequence, to yield a deoxygenated and isomerisedbase oil stream containing the renewable base oil.
 2. The methodaccording to claim 33, additionally for producing a naphtha fuel, wherethe naphtha fuel is obtained from distillation of both the deoxygenatedand isomerised base oil stream of step d) and from the distillation ofthe deoxygenated and isomerised diesel stream of step f).
 3. The methodaccording to claim 1, comprising: prior to step a), pre-treating aninitial feedstock containing fatty acid esters in at least a hydrolysisstep thereby producing the feedstock, where a ratio of free fatty acidsto fatty acid esters has been increased compared to the initialfeedstock.
 4. The method according to claim 33, wherein no pre-treatmentby hydrogenation or by hydrolysis is made in or in-between steps a)-c).5. The method according to claim 33, where the hydrodeoxygenation andhydroisomerisation of step d) take place in sequence, and wherein-between the hydrodeoxygenation and hydroisomerisation there is astripping step, where gasses are separated from liquids in a hightemperature and high pressure separation step at a temperature between300-330° C. and pressure between 40-50 barg.
 6. The method accordingclaim 33, wherein between steps d) and e) there is a stripping step,where gasses are separated from liquids, at a temperature between320-350° C. and pressure between 3-6 barg.
 7. The method according toclaim 33, wherein the free fatty acid feed mainly contains saturatedfatty acid or C₁₆ fatty acids.
 8. (canceled)
 9. The method according toclaim 33, wherein the feedstock is palm oil fatty acid distillate(PFAD).
 10. The method according to claim 33, wherein the ketonisationreaction conditions include a temperature in a range from 300 to 400°C., a pressure in a range from 5 to 30 barg and a WHSV in a range from0.25-3 h⁻¹, in a presence of a ketonisation catalyst, the ketonisationcatalyst containing a metal oxide catalyst, in a presence of a gas in arange from 0.1-1.5 gas/feed ratio (w/w), the gas being selected from oneor more of: CO₂, Hz, N₂, CH₄, and H₂O.
 11. The method according to claim33, wherein the ketonisation reaction conditions ensure liquid phaseketonisation; wherein the ketonisation catalyst is a metal oxidecatalyst selected from a list to contain metal consisting of one or moreof: Ti, Mn, Mg, Ca, and Zr.
 12. (canceled)
 13. The method according toclaim 33, wherein the ketonisation catalyst is TiO₂, in anatase formhaving an average pore diameter of 80-160 Å, and/or a BET area of 40-140m²/g, and/or porosity of 0.1-0.3 cm³/g.
 14. (canceled)
 15. The methodaccording to claim 11, wherein the ketonisation catalyst is TiO₂, on asupport, wherein a content of elements manganese, magnesium, calcium andpotassium, are 0.05 wt % or less compared to a total catalyst weight asmeasured using x-ray diffraction.
 16. The method according to claim 11,wherein the ketonisation catalyst is TiO₂, on a support, wherein acontent of the element potassium, is 0.05 wt % or less compared to atotal catalyst weight as measured using x-ray diffraction.
 17. Themethod according to claim 11, wherein the hydrodeoxygenation reactionconditions include a temperature in a range from 250 to 400° C., apressure in a range from 20 to 80 barg, a WHSV in a range from 0.5-3h⁻¹, and a H₂ flow of 350-900 nl H₂/l feed, in a presence of ahydrodeoxygenation catalyst NiMo on an alumina support.
 18. The methodaccording to claim 33, wherein the isomerisation reaction conditionsinclude a temperature in a range from 250 to 400° C., a pressure in arange from 10 to 60 barg, a WHSV in a range from 0.5-3 h⁻¹, and a H₂flow of 100-800 nl H₂/l feed, in a presence of an isomerisation catalystincluding a Group VIII metal and a molecular sieve, on an alumina and/orsilica support.
 19. The method according to claim 33, wherein thehydrodeoxygenation and isomerisation catalyst are the same; and whereinmore than 50 wt % of the feedstock is the mixture of free fatty acidsand fatty acid glycerols.
 20. (canceled)
 21. (canceled)
 22. (canceled)23. (canceled)
 24. The method according to claim 33, wherein thefeedstock comprises: at least 10 wt % and below 90 wt % free fattyacids.
 25. (canceled)
 26. (canceled)
 27. The method according to claim33, wherein the feedstock comprises: at least 10 wt % and below 90 wt %fatty acid esters.
 28. The method according to claim 33, wherein thefeedstock comprises: at least 10 wt % and below 90 wt % free fatty acidsand at least 10 wt % and below 90 wt % fatty acid esters, and whereinmore than 70 wt % of the feedstock is said mixture of free fatty acidsand fatty acid glycerols.
 29. The method according to claim 33, whereinsaid fatty acid esters are fatty acid glycerols.
 30. The methodaccording to claim 1, wherein the free fatty acid feed contains C₁₄-C₂₂fatty acids.
 31. The method according to claim 1, comprising: e)distilling the product of step d) to obtain a distilled renewable baseoil.
 32. The method according to claim 1, comprising: f) where the oneor more free fatty acid depleted feed(s) is transformed into a dieselproduct, by subjecting the one or more free fatty acid depleted feed(s)to both hydrodeoxygenation reaction conditions and to hydroisomerisationreaction conditions, simultaneously or in sequence, to yield adeoxygenated and isomerised diesel stream containing the diesel fuel;and distilling the stream obtained from step f) to obtain a distilleddiesel fuel.
 33. The method according to claim 31, comprising: f) wherethe one or more free fatty acid depleted feed(s) is transformed into adiesel product, by subjecting the one or more free fatty acid depletedfeed(s) to both hydrodeoxygenation reaction conditions and tohydroisomerisation reaction conditions, simultaneously or in sequence,to yield a deoxygenated and isomerised diesel stream containing thediesel fuel; and g) distilling the stream obtained from step f) toobtain a distilled diesel fuel.